1. Field of the Invention
The present invention relates to ultra-high speed photography technology, and more particularly to an optical-deflection accelerating device in ultra-high speed photography technology.
2. Description of the Related Technology
To obtain spatio-temporal information in microsecond to nanosecond transient-varying processes, for example, information for researching detonation physical process and shock-wave physical process, ultra-high speed photography technology has been developed. The ultra-high speed photography technology can be used to obtain photos of a transient-process in a microsecond-to-nanosecond time interval for studying variation rules of the transient process. The key technology of the ultra-high speed photography technology is how to generate a high speed and how to frame. That is, the key technology is how to obtain dozens to hundreds of photos which are varied over time in an ultra-short period.
Conventional ultra-high speed photographic methods first capture images, make light-beams of the images irradiate to a rotating mirror which rotates at a high speed, and then form high-speed deflections of emergent light-beams through the rotating mirror at the high speed, thus to high-speedily deflect the incident light-beams and perform a framing operation. A speed of deflecting the incident light-beams is a major issue related to performance of photography using the rotating mirror. Therefore, one of well studied subjects in the field involves speed improvement of deflecting the incident light-beams.
Currently, there are two methods for improving the speed of deflecting the light-beams. One method is making the incident light-beams irradiate to the rotating mirror which high speedily rotates, and improving the rotating speed of the rotating mirror to accelerate the deflection speed of the emergent light-beams. Another method is accelerating the deflection speed of the emergent light-beams through multiple reflections of the incident light-beams. In the method of improving the rotating speed of the rotating mirror, several ways, including using a high density material to be applied to the rotating mirror, improving a cross-sectional shape of the rotating mirror, improving a process technology in processing the rotating mirror, and improving a lateral structure of the rotating mirror, etc., can be used to accelerate the rotating speed of the rotating mirror. But this method is difficult to achieve multiplied acceleration of the rotating speed of the rotating mirror (HIGH POWER LASER AND PARTICLE BEAMS, 2006, 18(6):1277˜1281; SPIE, 2005, Vol. 5638:117˜123). The method of multi-reflection can multiply the deflection speed of the emergent light-beams.
Currently, the method of multi-reflection to accelerate the deflection speed of the emergent light-beams, can be performed by two schemes. One scheme is combining a rotating polyhedral reflective mirror with a static reflective mirror, and reflecting the light-beams between the reflective mirrors to achieve an acceleration of 4 times, 8 times or 12 times of the deflection speed of the emergent light-beams. Now there is an application using a nonagonal rotating mirror with a tetrahedronal reflector to achieve 4 times acceleration of the deflection speed of the emergent light-beams. Another scheme is reflecting the light-beams with a wedge-gap shape retroreflector, which is a combination of a moving mirror and a static mirror, or a double mirror in opposite directions. The light-beams can be reflected to 16 times acceleration of the incident light-beams, as determined by the wedge-gap shape device and the incident angle of the incident light-beams. Now, there is an application that achieves 7 times acceleration (SPIE, 2003, Vol. 4948:330˜335). The method of accelerating the emergent light-beams by multiple reflections must satisfy two conditions. One condition is that there must be an accurate rotating device, and another condition is that the light-beams must be multiple reflected by the reflective mirrors and the relative locations of the reflective mirrors must be accurate. However, the method of multi-reflection must be performed by accurate calculation, and the device thereof comes with a complex structure and a high cost.